Assay of L-lysine

Abstract

L-lysine contained in a sample can be efficiently determined by using the L-lysine α-oxidase. The preferred enzyme is an L-lysine α-oxidase, that is, a novel L-amino acid oxidase having very high substrate-specificity to L-lysine is produced by culturing a specific microorganism belonging to Trichoderma in a medium.

What is claimed is: 
     
       1. A method for determination of L-lysine in a sample, which comprises subjecting L-lysine contained in the sample to decomposition by the use of L-lysine α-oxidase in the presence of oxygen, and determining the quantity of oxygen consumed in the course of the decomposition or the quantity of hydrogen peroxide, ammonia, α-keto-ε-aminocaproic acid or Δ 1  -piperideine-2-carboxylic acid produced in the course of the decomposition. 
     
     
       2. The method for determination of L-lysine as set forth in claim 1, in which the L-lysine α-oxidase is an enzyme which is a product of aerobic culture of a strain belonging to the genus Trichoderma. 
     
     
       3. The method for determination of L-lysine as set forth in claim 1, in which the L-lysine α-oxidase is an L-amino acid oxidase having an ability to form α-keto-ε-aminocaproic acid, ammonia and hydrogen peroxide from L-lysine by oxidative deamination of L-lysine in the presence of water and oxygen as well as having a very low Km value with respect to L-lysine and the high substrate-specificity with respect to L-lysine. 
     
     
       4. The method for determination of L-lysine as set forth in claim 3, in which the coenzyme thereof is flavin adenine dinucleotide. 
     
     
       5. The method for determination of L-lysine as set forth in claim 3 or 4, in which the enzyme has a molecular weight represented by two subunits each having a molecular weight of 56,000 (±5,000) determined according to an electrophoresis method using SDS-polyacrylamide gel, a molecular weight of 112,000 (±10,000) determined according to a gel filtration method, and a molecular weight of about 119,000 determined according to ultracentrifuge sedimentation equilibrium method.